1. Field of the Invention
The present invention relates to a fuel cell stack including a stack body formed by stacking a plurality of power generation cells in a stacking direction. Each of the power generation cells is formed by stacking a membrane electrode assembly and a separator. The membrane electrode assembly includes a pair of electrodes and an electrolyte membrane interposed between the electrodes. End plates are provided at both ends of the stack body in the stacking direction.
2. Description of the Related Art
For example, a solid polymer electrolyte fuel cell employs a polymer ion exchange membrane as an electrolyte membrane, and the polymer electrolyte membrane is interposed between an anode and a cathode to form a membrane electrode assembly (MEA). The membrane electrode assembly and a pair of separators sandwiching the membrane electrode assembly make up a power generation cell for generating electricity. In use, typically, a predetermined number of the power generation cells are stacked together to form a fuel cell stack, e.g., mounted in a vehicle.
In the fuel cell stack, internal manifolds are often adopted for supplying a fuel gas and an oxygen-containing gas as reactant gases to the anode and the cathode of each of the stacked power generation cells. The internal manifold includes reactant gas supply passages and reactant gas discharge passages extending through the power generation cells in the stacking direction.
In the case where the fuel cell stack is, in particular, mounted in a vehicle, a considerably large number of power generation cells need to be stacked together. Therefore, the power generation cells need to be positioned accurately. For example, a method of assembling a fuel cell disclosed in Japanese Laid-Open Patent Publication No. 09-134734 is known.
In the assembling method, as shown in FIG. 10, positioning holes 3 for assembling cells 5 are formed in a pressure application plate 2 for applying pressure to a stack 1. Elongated knock pins 4 having chamfered end surfaces, made of PTFE are inserted upright into the positioning holes 3. Then, the cells 5 having the positioning holes 3 are stacked together successively such that the positioning holes 3 of the cells 5 are fitted to the knock pins 4 to form the stack 1. Thereafter, components of the stack 1 are fixed tightly.